[Heory]

That's close.I think it is the O2 in the atomosphere that dehydrogenated the intermediate. As for the electrocyclic reaction, you'd better leave the seperated charges as it were. Don't draw the 3-memered cycle. But essentially you are right. Would mind drawing the whole mechanism for this problem?

[tmartin]

I actually did not save any of my schemes as ChemDraws this time around... but if I get bored later in the day I may find time to redrawn them all...if not I'll leave it to you 

Is there a reference to this problem?  It would be interesting to see what led to this discovery, and also what type of yields are obtained.

[Heory]

I don't have the original document. But just now I found its tittle frow which we can see the reaction was just a surprise and the oxidant was the tetrazine.